Our previous research on the Wechsler Adult Intelligence Scale (WAIS; NIA grants AGO2695, AG0474, and AGO74O7) has produced: (1) a large-scale data base of WAIS information useful for aging research, (2) some novel structural equation models appropriate for aging research, (3) some results about the complex measurement functions of the WAIS, and (4) some results about the complex growth curve functions of intellectual ability. During the past two years of this project we have tested a strategically selected set of adults who have already been tested before on a wider battery of ability measures. This includes the collection of three-wave longitudinal retest data on the large National Growth and Change Study (NGCS) sample, and the sixth-wave of longitudinal data on the smaller Bradway sample. Our new analyses are focusing on the leading and lagging indicators of dynamic aging processes, especially for different groups of persons. In this competing continuation proposal we continue to use new statistical methods for the synthesis of research on the measurement and growth curves of intellectual abilities. We base all analyses on structural "convergence models" using "planned missing" subjects, occasions and variables. We also implement an experimentally efficient data collection plan to collect critical missing adult abilities data. In the current project we will recruit and retest three different samples spread across all geographical areas of the USA. Subjects with a pre-specified retest lag period between 4 and 10 years will be sampled to examine individual differences in cognitive changes, including the following three groups: (1) N=55 subjects aged 64-68 from the Bradway-McArdle longitudinal sample - These persons are now about 64 years of age and have been tested on intellectual abilities since they were 4 years old (last tested in 1992). (2) N=200 adults aged 19 to 95 years who have been tested before on the WAIS or the Woodcock-Johnson (WJ) tests of intellectual ability (last tested in 1986 or 1992). (3) N=200 adolescents aged 18 to 24 from the previous NGCS national sample who have already been tested twice before on the WJ-R test battery at ages 12 to 18 (last tested in 1986). In all samples we will use an extensive battery of ability tests, including parts of the standard WAIS, the Woodcock-Johnson Revised (WJ-R) test of abilities and achievements, and out NGCS demographic questionnaire. This is a continuation of our previous work in several ways. First, based on our previous findings, we will recast substantive theory about intellectual development into testable models. Second, we will further develop mathematical and statistical models for growth and change required to deal with the complex set of WAIS and NGCS data. Third, we will collect some new data that will allow us to more effectively use latent variable structural equation models. This plan will help us identify both the factors of measurement and the factors of change, unravel the dynamics effects of multiple growth and retest processes, and separate the direct from the indirect exogenous effects on these intellectual ability factors. These new results will synthesize all past research on the WAIS and provide valuable information for further research on the growth and decline of intellectual abilities across the entire adult life-span.